completely and udderly WRONG. you divide your box in half(on paper) and calculate 1 port per 'box'.Just do the calculations the same way you would for a box with a single port, only the specs of the single port come from two ports added together. Port area, length, and displacement must be added together from each port to get the total.
Thank you!//content.invisioncic.com/y282845/emoticons/graduate.gif.d982460be9f153bb54e5d4cb744f6ae8.gifcompletely and udderly WRONG. you divide your box in half(on paper) and calculate 1 port per 'box'.
only if the box is going to be divided... if its all one open area, the ports need to be calculated together, right?completely and udderly WRONG. you divide your box in half(on paper) and calculate 1 port per 'box'.
one thing that i just cannot stand, is people spreading mis-information. i'm pretty smart...but if i'm not for positive, i wont guess. i'll let you know.Thank you!//content.invisioncic.com/y282845/emoticons/graduate.gif.d982460be9f153bb54e5d4cb744f6ae8.gif
lets see if it works.....i don't believe it will....The way I was told is take the NET volume of the entire box. Take the total port area (both ports) and then figure your port length. Divide it in half and each of your ports should be that long...this is for a single chamber box btw, a dual chamber box is obvious....just design two boxes.
very well put. i didn't feel like going that in depth. but now maybe people can comprehend...lets see if it works.....i don't believe it will....
for numbers sake, let use a 4cu' tuned to 30Hz. our ports will be 2 ports each at 2" x 12" so 24sq" each...and 48sq" total...
if you divide the box by the numbers of ports first......
Lv = [(14630000 x 7.64) / (900 x 3465)] - (1.463 x 2.76)
Lv = (111773200 / 3118500) - 4.04
Lv = 35.84 - 4.04
Lv = 31.0
now lets add the port area to get our 48sq" and use the total box volume...
Lv = [(14630000 x 15.28) / (900 x 6912)] - (1.463 x 3.91)
Lv = (223546400 / 6220800) - 5.72
Lv = 35.94 - 5.72
Lv = 30.22
now you say to divide this by 2 and you get...
Lv = 15.11
as you can see the results are very different from each other.
YOU MUST DIVIDE THE BOX BY THE NUMBER OF PORTS FIRST AND FIGURE IT OUT FOR EACH PORT.
That's the part that explains why this occurs for anybody wondering. I learned something today.Notice that Method 1 produces the same port length as did our single 4" diamter port as it should (after all, we have the same total port cross-sectional area which this school of thought proclaims is correct!). But the first method is incorrect because it neglects the frictional losses encountered by using many smaller ports--there is a higher port wall surface area to cross-sectional area ratio which raises the total amount of frictional losses in the ports and thus shifts the tuning!